1. Field of the Invention
The present invention relates to a deforming mechanism for deforming a transmissive optical element, an exposure apparatus including the deforming mechanism, and a device manufacturing method of manufacturing a device using the exposure apparatus.
2. Description of the Related Art
As a mechanism for correcting non-rotational symmetrical on-axis aberration of the projection optical system of an exposure apparatus, a deforming mechanism is conventionally used which corrects the aberration of the whole projection optical system by deforming a transmissive optical element included in it.
Japanese Patent Laid-Open No. 2002-519843 or 2000-195788 discloses a deforming mechanism which applies a translational force alone or both a translational force and a torque to two opposing portions of a transmissive optical element, thereby deforming it.
In the prior-art deforming mechanism for deforming the transmissive optical element, the translational force is transmitted to the light passing area of the optical element when deforming it. This causes birefringence, resulting in degradation in optical performance.